在wordpress中的Tools选项中安装wordpress导入器后，当我尝试激活它时，会出现致命错误。

相关php代码：

class WXR_Parser {
    function parse( $file ) {
        // Attempt to use proper XML parsers first
        if ( extension_loaded( \'simplexml\' ) ) {
            $parser = new WXR_Parser_SimpleXML;
            $result = $parser->parse( $file );

            // If SimpleXML succeeds or this is an invalid WXR file then return the results
            if ( ! is_wp_error( $result ) || \'SimpleXML_parse_error\' != $result->get_error_code() )
                return $result;
        } else if ( extension_loaded( \'xml\' ) ) {
            $parser = new WXR_Parser_XML;
            $result = $parser->parse( $file );

            // If XMLParser succeeds or this is an invalid WXR file then return the results
            if ( ! is_wp_error( $result ) || \'XML_parse_error\' != $result->get_error_code() )
                return $result;
        }

        // We have a malformed XML file, so display the error and fallthrough to regex
        if ( isset($result) && defined(\'IMPORT_DEBUG\') && IMPORT_DEBUG ) {
            echo \'<pre>\';
            if ( \'SimpleXML_parse_error\' == $result->get_error_code() ) {
                foreach  ( $result->get_error_data() as $error )
                    echo $error->line . \':\' . $error->column . \' \' . esc_html( $error->message ) . "\\n";
            } else if ( \'XML_parse_error\' == $result->get_error_code() ) {
                $error = $result->get_error_data();
                echo $error[0] . \':\' . $error[1] . \' \' . esc_html( $error[2] );
            }
            echo \'</pre>\';
            echo \'<p><strong>\' . __( \'There was an error when reading this WXR file\', \'wordpress-importer\' ) . \'</strong><br />\';
            echo __( \'Details are shown above. The importer will now try again with a different parser...\', \'wordpress-importer\' ) . \'</p>\';
        }

        // use regular expressions if nothing else available or this is bad XML
        $parser = new WXR_Parser_Regex;
        return $parser->parse( $file );
    }
}